The present invention relates generally to polymeric laminate constructions and is more particularly concerned with a flexible acoustical laminate construction specifically adapted for application to noisy enclosure surfaces, thereby to attenuate deleterious noise within such enclosures.
Operators of heavy construction, industrial, mining and transportation equipment such as bulldozers, power shovels, trucks, graders, pugmills, jaw crushers, blasthole drills, wheeled front-end loaders, haulers, diesel powered shovels and draglines and the like are often subjected to noise levels of sufficient intensity as to be harmful to hearing. This is particularly so where such noise exposure is experienced on a chronic, day-to-day basis. There usually exist in such equipment three general pathways or mechanisms by which sound is transmitted into the operator or crew cabs thereof. Airborne sound can, of course, enter the cab from the exterior through openings in the cab. Sound, generated as mechanical vibrations by prime movers, hydraulic mechanisms and other ancillary equipment, can also be transmitted directly through the structure of the equipment and radiated therefrom into the cab. Also, sound can be introduced into the cab by excitation of the cab structure(s), such as sheet metal panels, by impingement of external noise thereon. Once sound has entered the cab, by whatever the mechanism, the intensity thereof can be amplified by airborne reflection within the cab structure. To a certain extent, this last-mentioned phenomenon of internally reflected sound is beneficial since this can represent a major source of sensory information by which the skilled equipment operator is enabled to monitor engine and hydraulic loads and to hear voice commands and conversation within the cab. Accordingly, it is a desideratum of the present invention to provide an acoustic laminate construction which, when suitably affixed to a noisy heavy equipment crew enclosure or operator cab, results in an overall substantial reduction of deleterious noise levels while preserving the capacity of the operator or crew to hear those sounds beneficial to effective and safe operations of the equipment.